|Year : 2016 | Volume
| Issue : 2 | Page : 93-100
Sport-related renal injuries among children: A review of literature
Hamdan Hammad Alhazmi
Department of Surgery, Division of Urology, College of Medicine, King Khalid University Hospital, King Saud University, Riyadh, Saudi Arabia
|Date of Web Publication||13-Apr-2016|
Dr. Hamdan Hammad Alhazmi
Department of Surgery, Division of Urology, College of Medicine, King Khalid University Hospital, King Saud University, Riyadh
Sport-related renal trauma among children is a type of injury results usually from a blunt abdominal trauma during nonorganized sport. It can happen during either individual sports such as cycling, skating, skiing, sledding, snowboarding, gymnastics, and horseback riding or in clash sports such as football, rugby, soccer, martial arts, and ice hockey. Trauma may lead to hematuria, hemorrhage, thrombosis, renal artery occlusion or destruction, and tissue disruption of parenchyma and collecting ducts. Children are more susceptible to renal trauma due to anatomical variations from adults. Most injuries are managed conservatively with renal preservation. It is estimated that Sport-related renal trauma was 1-3% among children between 5 and 15 years in age. This narrative review article presents an overview of the current knowledge of sport-related renal trauma among children after review of 56 research paper focusing on etiology, pathophysiology, diagnosis, safety measures, and treatment. This information should assist healthcare practitioners who treat patients with this type of injury. Safety measures help in avoidance of such trauma and protect from unpleasant squeal.
إصابات الكلى المتصلة بالرياضة بين الأطفال: مراجعة الأدبيات
إصابات الكلى المتعلقة الرياضة بين الأطفال هي نوع الإصابة التى عادة تحدث من صدمة حادة في البطن اثناء الرياضة ويمكن أن تحدث خلال الرياضة الفردية مثل ركوب الدراجات، التزلج،التزلج على الجليد، والجمباز، وركوب الخيل أو في الرياضة الجماعية مثل كرة القدم والركبي وكرة القدم، فنون الدفاع عن النفس، وهوكي الجليد. والصدمة الناتجة قد تؤدي إلى كدمة دموية، نزيف، تخثر الدم وانسداد الشريان الكلوي أو تدمير وتعطيل الأنسجة . والأطفال هم أكثر عرضة لإصابة الكلى بسبب الاختلافات التشريحية من البالغين. وتعالج معظم الإصابات بالعلاج التحفظي مع الحفاظ على الكلى. وتشير التقديرات إلى أن صدمة الكلى الرياضية هى ذات الصلة لدى 1-3٪ من الأطفال ما بين 5 و 15 سنوات في العمر. تقدم هذه المقالة لمحة عامة عن المعرفة الحالية عن إصابات الكلى المتصلة بالرياضة بين الأطفال بعد مراجعة 56 ورقة بحثية عن المسببات، الفيزيولوجيا المرضية والتشخيص وإجراءات السلامة، والعلاج. هذه المعلومات تساعد ممارسي الرعاية الصحية الذين يتعاملون مع المرضى الذين يعانون من هذا النوع من الإصابات. كما أن تدابير السلامة تساعد في تجنب مثل هذه الصدمات والحماية من النتائج الغير حميدة.
Keywords: Blunt abdominal trauma, renal injuries, sport
|How to cite this article:|
Alhazmi HH. Sport-related renal injuries among children: A review of literature. Saudi J Sports Med 2016;16:93-100
| Introduction|| |
Kidney injury in children is more common after significant blunt abdominal trauma.  It may occur during vigorous exercises and harsh sports.  Most injuries are managed conservatively with the advances in imaging and known more about the natural history of the genitourinary tract injuries.  Renal injury is the most common type of injuries in the genitourinary tract in children.  Renal injury during exercise usually results from blunt trauma more than penetrating injuries.  Variation in anatomy, preexisting renal anomalies as well as the presence of renal disease, make children more susceptible to kidney injuries. 
| Biomechanics|| |
Kidneys are relatively mobile organs so injury might occur by contusion, in spite of being well protected inside the body.  Kidney of a child with an age range of 5-15 years is more susceptible to traumatic injury due to the immature pliable thorax which protects it, as well as the weak abdominal and flank muscles.  In comparison to an adult kidney, the child's kidney shows less perinephric fat and the retroperitoneal space has the comparatively low amount of peri-peritoneal fat. ,
In relation to the abdominal size in pediatrics, the kidney is relatively large than in adults. The lower poles of kidneys in children are protruding inferiorly beneath the 12 th rib. The low setting position of the kidney makes it more prone to injury.  Those contributing factors would play an important role in transmitting the force of blunt trauma completely to the kidney, especially if the trauma occurred in the upper abdominal quadrants. Kidneys of children are characterized by poorly developed Zukerkandl fascia, renal capsule, and Gerota's fascia. Pronounced kidney lobulations may make their kidneys more prone to parenchymal tears. 
The presence of congenital malformations in the kidney may play an important role in increasing susceptibility of renal injury, due to more anatomical distortion. The incidence of renal injury among children with congenital renal anomalies is ranging from 5% to 24%.  It was found in the literature that children with solitary kidney were subjected to more damage and failure of renal preservation after renal trauma.  Compensatory hypertrophy associated with the solitary kidney increases the surface area of the kidney, which results in more susceptibility to renal trauma. Furthermore, children with horseshoe kidneys and ureteropelvic junction (UPJ) obstruction tend to have a higher incidence of renal injuries with minor blunt trauma than others with normal kidneys. 
Preexisting renal diseases such as; renal hypertrophy, renal vascular diseases, renal failure, and hydronephrotic changes which occur as complications of systemic diseases such as hypertension, chronic heart failure, diabetes, multiple myeloma, chronic infection, and autoimmune diseases. Those systemic diseases are considered as contributing factors that increase the probability of renal injury after abdominal trauma by 10%. ,
| Incidence|| |
Organized sports are rarely to cause serious renal injury. Notably, renal trauma usually occurs in association to other organ injuries in about 80% of all grades of kidney injuries and rarely occurs in isolation. , In a review of 50,000 children trauma cases, it was found that 21% of them had significant blunt abdominal trauma. Renal injury with different grades happened in 10.6% of them and 3% of them had sport-related renal injury, with male-to-female ratio of 9:1. 
The literature showed the incidence of renal injury in children accounts for 10% of all significant blunt abdominal traumas. Renal injuries account for more than 60% of genitourinary injuries in children. , In children, blunt abdominal trauma happens more often than penetrating injuries.
A study evaluated 400 renal injuries among children has shown that 90% were due to blunt trauma, and 10% were penetrating. 
The incidence of renal injuries resulted from sports and exercises are 1%. Only 2 of 194 pediatric kidney injuries resulted from sport, one of them had congenital ureteropelvic obstruction and the other is normal; both of them had blunt traumas and grade II renal injury.  Another retrospective study done on 770 cases of kidney injuries among children, road traffic accidents involved in 96% of cases; however, the remaining trauma were attributed to football (0.6%), hockey (0.2%), horse riding (0.8%), bicycling (1.2%), and falls (3.2%). Renal injury during bicycling showed high damage, were almost 70% of cases were grade IV and V, kidney could not be preserved in two cases. 
In 139 patients with grade III, IV, and V injury according to the American Association for the Surgery of Trauma (AAST) renal injury scale; 0.2% was sport-related and 99.8% were not. In particular, males are more prone to injury than females (90% vs. 10%; P < 0.001), most probably due to their testosterone-related aggression and risky activities. Nonsport-related injuries are more severe than sport-related injuries. Sport-related injuries are associated with grade III (57.9% vs. 49.4%) whereas nonsport-related injuries are associated with grade IV and V (39% vs. 30%). 
| Etiology|| |
The kidney is the third most common solid intra-abdominal organ which is subjected to injury due to blunt abdominal trauma. Similar to spleen rupture, kidney injury caused by a direct abdominal blow, either from the side or the back (above the loin). Injury occurs in the form of damage or tear. This usually seen with vigorous nonorganized sports with high contact such as; rugby, soccer, martial arts, ice hockey, and football or some individual sports-due to falls and accidents-such as bicycling, skating, skiing, snowboarding, sledding, gymnastics, and horseback riding. ,
High-contact sports among children are not too vigorous to cause renal trauma, however; falls and hard collision to solid objects in high-speed individual sports are the most common causes of sport-related renal trauma in children.
Injuries result from high-contact sports are usually low-grade renal in severity. They are caused by blunt trauma that comes from a direct blow to the back or the flanks by helmet, knees, shoulder pads, or any object used in martial arts. Those types of trauma are very rare among children due to their weak body built and less aggression in high-contact activities. Falls and accidents result from individual sports such as cycling, horse riding, and winter sports, lead to high-grade renal injuries. Those types of injuries are more common among children, (0.8% vs. 5.2%, P < 0.01), respectively. ,
In a study evaluated 14 injuries, bicycling was the most common cause, accounting for 9 of 14 cases. All of those injuries were falls, and none of them came from motor vehicle accident. Regarding the severity of injuries, it was grade I in 1 case, grade II in 1 case, grade III in 1 case, grade IV in 3 cases, and grade V in 3 cases. Sledding, hockey, and football were responsible for the remaining injuries. Handlebars of the bicycle were the main factor leading to blunt abdominal trauma and the renal injury happened in 3 cases. The kidney could not be preserved in 1 case of bicycle-related trauma.
Kickboxing is one of the most common causes of sport-related renal injury in adults, through direct blow in the flanks below the ribs. There is other activities could cause renal related injuries like skiing, cycling, and snowboarding. 
In another study, it was found that sport related high-grade renal injury was more likely to be isolated without any other organs injury. Hemodynamic instability is associated with nonsport-related trauma that requires intervention. The renal injury caused by motor vehicle accidents during sports are not classified as sport-related renal trauma. ,
| Injury Classification and Pathogenesis|| |
Blunt abdominal trauma can lead to tissue loss and/or tissue disruption of the parenchyma and collecting ducts. Abdominal computed tomography (CT) scan, and surgical exploration finding are used for the classification of renal injury, according to the system of the American Association for the Surgery of Trauma (AAST) [Table 1].  It is a validated classification scale for renal injuries to help in predicting the prognosis and guide surgeons and help them in making the treatment decisions. It also helps in the prediction of morbidity and mortality after injury and the extent of need for operative intervention. 184 cases of renal injuries out of 230 cases (80%) present in the form of renal contusion, which is classified as grade I renal injury with decrease uptake of contrast material. Renal contusions characterized by less pain and nausea. Renal parenchymal laceration <1 cm and >1 cm are classified as grade II and III respectively as long as there is no extension to the collecting system and no urine extravasation. Bilateral injuries of grade 1 rise the grading up to III. Lacerations limited to the parenchyma and not extending to the collecting system are considered as minor lacerations. Lacerations cause space occupying hematoma may lead to more pain and nausea. 
A laceration that involves the collecting system or hilar vessels are considered major lacerations and classified as grade IV injuries which accompanied by urine extravasation and required delayed imaging by CT scan for accurate diagnosis. It might be associated with more bleeding and more pain with or without hemodynamic instability.
Renal vascular injury occurs in <4% of cases. Isolated renal artery injury occurs in <0.05% of cases. Thrombosis and renal artery occlusion caused by a hemorrhage in the wall of the vessel, which occur due to intimal tear, stretching of adventitia and muscularis mucosa caused by vascular traction. This may lead to compromised and asymmetric renal perfusion compared to the other healthy kidney. Renal artery occlusion also may result from compression of the artery between the abdominal wall and the vertebrae. 
Grade V injury is characterized by fragmentation of renal tissue which is called "shattered kidney" with severe contusion, devitalization, devascularization, hemorrhage, and urine extravasation. Grade V renal injury is usually managed surgically with exploration and very high chance of nephrectomy.
Although nephrectomy is the treatment of choice in pedicle injuries, renal salvage can be an option in some cases <30%.
| Clinical Picture|| |
Early diagnosis and proper treatment are the golden clues in renal preservation and avoidance of trauma-related complications. The sport-related renal injury is more common in male children between ages of 5 and 15 years, who had a positive history of recent blunt abdominal trauma during sport. Most common activities associated with such traumata are bicycling, skating, skiing, snowboarding, sledding, gymnastics, and horseback riding. Special concern should be for those with congenital anomalies and preexisting renal diseases which may complicate minor injuries. 
Vital signs are of high value in such patients, and they should be recorded for detection of any signs of hemodynamic instability. Hypotension is a rare sign in children because of the gush of catecholamines to maintain blood pressure in spite of significant blood loss. High sympathetic tone and absence of a relation between hematuria and severity of injury make the diagnosis depending on the clinical picture and associated injuries.
Abdominal, flank, and back inspection and examination is very important, for detection abrasions, ecchymosis, fractured ribs, abdominal distension, renal mass, and tenderness. 
| Complications|| |
Early complications can occur within 1 month after the injury such as infection, bleeding, fistula, perinephric abscess, sepsis, urinoma, and urine extravasation. Delayed complications such as calculus, hydronephrosis, pyelonephritis, hypertension, arteriovenous fistula, pseudoaneurysms, and retroperitoneal bleeding can occur after 1 month from injury. 
Hypertension is a rare posttraumatic sequel, especially among children as it can happen in <5% in children after injury. It occurs either early, due to external compression of hematoma on renal vasculature or later on, due to external compression by fibrotic scar. Renin-mediated hypertension occurs as a result of vascular insult, the formation of fibrous capsule surrounding the injured kidney, and the presence of devitalized renal segments. Renin-mediated hypertension results from diminished perfusion due to parenchymal compression by hematoma or urinoma (Page kidney), also in cases of renal artery stenosis leading to renal ischemia and release of unleashed renin (Gold blatt kidney). One of the causes of renal ischemia linked to renal trauma is a persistent posttraumatic arteriovenous fistula. 
Delayed onset bleeding may occur after 1-4 weeks from the trauma. It is common among patients with grade III and IV who were managed conservatively, it could happen in >25% of those high-grade injuries. Devitalized parenchyma, hematoma, and urinoma are common causes of infection, abscesses and sepsis.
Urine extravasation results from disruption of UPJ or from tears extending to the collecting system. Complete UPJ avulsion may occur as a result of fall from heights. Seventy percent of urinomas associated with renal injury have shown spontaneous resolution with no management, and over 90% of children who had grade IV injury improved by conservative management. Arteriovenous fistulae, duodenal obstruction, and development of pseudoaneurysm are rare complications after blunt trauma. ,
| Investigations|| |
Microscopic or gross hematuria can be detected by urinalysis; however, it is neither specific nor sensitive sign in the grading of renal trauma.  Hematocrit value could be of high value in diagnosis.  High-grade renal injury such as segmental arterial thrombosis, pedicle injuries, or disruption of the UPJ can even occur without hematuria in 10% of cases. , Hematuria with positive history of blunt abdominal trauma is highly indicative for renal injury and further radiological workup; however, it may suggest preexisting renal disease if there was no history of trauma.  Hematuria can be detected by urine dipstick as a rapid reliable test; however it may show false negative results in about 3-10% of cases.  The rate of blood loss can be monitored indirectly by serial hematocrit value, the requirement for blood transfusion and vital signs, as indicators for patient's response to resuscitation. Monitoring of blood loss is also valuable in decision making, either to be managed conservatively or require urgent intervention. 
Creatinine level is a good indicator of the baseline and postrenal trauma function. Creatinine could be still within normal ranges after injury by 1 h, so early diagnosis and proper treatment are golden clues in renal preservation because elevated creatinine level reflects drop in renal function, in case of bilateral renal injury, urine leak, or shock.  Some studies on animal models have shown that serum creatinine remains normal within 8 h post bilateral nephrectomy. 
| Imaging and Radiographic Assessment|| |
Most of the cases with renal trauma are trivial and managed with observation without any intervention. Clinical picture and mechanism of injury may influence the decision of the need for imaging. Imaging itself causes discomfort, allergy, and exposure to radiation, in addition to expenses and time.  Radiological evaluation should be used in cases of gross hematuria or microscopic hematuria with hemodynamic instability or if there are major associated injuries.  Immediate imaging is required in the presence of signs and laboratory findings of renal trauma. Imaging is useful to rule out pedicle injury or ureteral avulsion.  Penetrating injuries usually are associated with significant injuries, regardless of the degree of hematuria; imaging in such cases is indicated. 
Ultrasound (US) is a useful tool for assessment of blunt injuries. It is a noninvasive, rapid investigation at low cost to detect peritoneal fluid collections, hemoperitoneum, and hemopericardium.  It can detect lacerations without an accurate assessment of extent and depth. It can evaluate parenchymal lesions, retroperitoneal hematomas or follow-up of stable injuries for urinoma and hematoma resolution. Hence, US is used in cases presented with the triad; the child had a positive history of blunt abdominal trauma with microscopic or gross hematuria. It can be the first and simplest radiological scan to identify patients who need further radiological investigations. The US does not provide information about urine leakage or excretion. Contrast-enhanced US is more sensitive than the conventional US. 
Intravenous pyelography (IVP) is used to identify nonfunctioning kidney and extravasation which are signs of high-grade renal trauma, avulsion, thrombosis, or shattered kidney. It is used to evaluate the integrity of the capsule, outline the collecting system and define the renal parenchyma. IVP is less sensitive than CT scan. Hence, it is recommended in the absence of other diagnostic tools.  Further radiographic assessment should be done in case of incomplete filling, obscuring of the renal shadow, caliceal distortion, nonvisualization, contrast extravasation, contour deformity, and delayed excretion. One-shot intraoperative IVP can be done in hemodynamically unstable patients having an emergency laparotomy to guarantee the function of the other noninjured kidney. 
CT is the investigation of choice for assessment of renal trauma. It is highly sensitive and specific test. It gives accurate information about the location of the injury, presence of contusion, the depth of the lacerations and the extent to the collecting system, the presence of urine extravasation, the presence of devitalized segments or retroperitoneal hematoma, and to assess for associated abdominal injuries.  It could easily detect preexisting renal diseases and renal anomalies. The presence of large hematoma displacing the vasculature medial to the kidney could indicate renal vein injury. Lack of enhancement or central para-hilar hematoma could be a sign of renal pedicle injury. Good parenchymal enhancement does not exclude pedicle injury.  Few artifacts and short scanning time are advantages of spiral CT, so in the case of complex lacerations, vascular pedicle assessment, noncooperative patients, and injuries of the collecting system, spiral CT is the investigation of choice. Repeated spiral CT scans within 15 min of contrast injection could be valuable to avoid missed diagnosis in collecting system injury.  Delayed excretory CT scan could be beneficial in the diagnosis of injuries of ureter and UPJ. Magnetic resonance imaging requires a longer imaging time, so it is not recommended in trauma patients. It is useful only in case of allergic patients to iodine, unavailability of CT scanner or if CT scans findings were equivocal. 
CT Angiography is more invasive, more time-consuming, and less specific than ordinary CT scan. However, it is useful to define degree and location of venous injuries and extravasation.  CT Angiography is valuable in case of cortical nonenhancement by ordinary CT, caused by total vascular avulsion, vascular spasm, or renal artery thrombosis. If the patient had an allergy to iodine contrast, radionuclide scans are recommended instead of CT scan to assess for renal uptake. 
| Treatment|| |
Low-grade renal injuries (I-III) could be managed conservatively in 85% of cases in blunt trauma. The main goal is renal preservation and prevention of complications.  Bed rest, vital signs monitoring, and limited activity for 2-6 weeks until hematuria and hematocrit resolved and stabilized.  Follow-up with US and CT for deteriorated patients can detect complications, indicating exploration, renal repair, ureteral stenting, and angioembolization.
High-grade renal injuries (IV-V) could be managed conservatively in hemodynamically stable patients because surgical intervention results in nephrectomy in >85% of cases. Only cases with shattered kidney, vascular pedicle injury, pulsatile or expanding retroperitoneal hematoma or failure of angioembolization to stop hemorrhage should be managed surgically for fear of life-threatening hemorrhage, major complications or loss of renal function.  Expanding hematoma, urine extravasation, devitalized renal tissue, and vascular injuries are relative indications for surgical exploration. The goals of the surgical intervention are to ensure hemostasis and debridement of devitalized renal tissue and to assess and repair any collecting system lacerations. Salvage should be avoided in bilateral renal injuries or renal injuries for children with a solitary kidney unless there were extreme circumstances which require lifesaving nephrectomy. 
Conservative approach of low-grade renal injuries usually leads to complete healing. High-grade injuries and shattered kidneys associated with 35-40% renal volume loss, could remain viable, retain blood supply and rearchitect themselves in proper alignment in spite of having persistent morphological deformities such as scars. 
Retroperitoneal hematoma could be a life-threatening sequel of renal injury, and selective angioembolization is the treatment of choice. Percutaneous drainage of perinephric collection or abscess is preferred to open drainage because percutaneous management of complications has a low risk of renal loss. Percutaneous management reduces the probability of infection in case of perinephric urinoma. Hypertension could be managed medically or by vascular reconstruction, excision of the ischemic renal segment, or even nephrectomy. Antihypertensive medication is valuable till the underlying cause resolves spontaneously; however, the duration and outcome of treatment are unknown so surgery might be the ultimate solution. As long as infection and obstruction is not present, reconstruction of extravasation could be successful. Retrograde stenting of the ureter and/or percutaneous drainage promote healing and improve drainage in cases of urine extravasation related to the collecting system injuries. 
Postoperative care and follow-up is crucial in all trauma patients with renal injuries.
The follow-up is more important in patients with high-grade injuries who were treated conservatively to prevent complications as the risk of complications increases with high-grade injuries. Repeating the imaging after the conservative approach is a key step in following those patients after renal trauma. In patients with high-grade injury who are managed with observation, serial hematocrit and repeating their imaging is an important aspect of their care during the admission. Repeating the imaging after discharge as part of the follow is necessary too.
Nuclear scans can be used for follow-up of patients after renal reconstruction to evaluate renal function. Measuring of blood pressure should be continued for years to detect latent hypertension. 
| Conclusion|| |
Sport-related renal injury in childhood may lead to renal loss. This type of injury poses a high risk on child's life if it is left undiagnosed or complicated although conservative management in most of the cases is highly successful, especially in children subjected to sport-related renal trauma. ,,,, Some individual sports such as bicycling, skating, skiing, snowboarding, sledding, gymnastics, and horseback riding are the main causes of such type of injuries especially if they were nonorganized. ,,,, Blunt abdominal traumata are the most common causes of renal injury among children, so clinical picture, as well as laboratory investigations and scanning, are very important to detect renal injury among those cases. ,,,,
| Recommendations|| |
- High contact sports, as well as some individual sports characterized by high speed, should be well organized and covered completely by safety precautions and protocols to avoid such type of injury
- Hemodynamic instability in a child with history of blunt abdominal trauma accompanied by gross or microscopic hematuria should be investigated meticulously for renal injury
- Medical care personnel should be aware if of any history of congenital renal anomalies or preexisting renal disease because they are highly susceptible to renal trauma and complications
- Further research should be conducted in this topic, for innovation and suggestion of safety measures during individual and contact sports to avoid blunt abdominal trauma.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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